Strainer for pulp digesters



Feb. 8, 1944. c. K. BOYER STRAINER FOR PULP DIGESTERS 2 Sheets-Sheet 2 Filedl May 25, 1940 mwN OOOOOOOOO OOOOOOOOO O OO OO OOOOOOO o o o o o o o o o o o o o Q o o o o O o o o o o o O o o o o o o o OOO OOO \OOO o o Patented Feb. 8, v1944r '2,340,925 STRAINER FOR PULP DIGESTERS Cheney' K. Boyer, Appleton, Wis., assignor to Consolidated Water Power & Paper Company, Wisconsin Rapids, Wis., a corporation of Wisconsin Application May z5, i940, serrer No. 337,174

' (o1. raz-7) Claims.

This invention relates to improvements in chemical pulp digesters particularly adaptable for the manufacture of chemical pulp employed in the making of paper, and refersspecically to a strainer construction Autilized in conjunction with a chemical pulp digester.

It is the usual practice in the cooking of` chemical pulp to relieve or withdraw from the pulp digester a portion of the gases or liquors from the digester for recovery of said gases or liquors or for the purpose of re-heating the same outside the digester and returning them to the digester.- Such practice requires the use of a device commonly known to the art as a strainer which permits the gases and liquors to ow from the digester, but strains out and vdeposits frequently form on the strainer plates causing the perforations therein to be clogged. This necessitates frequent periodic cleaning.

" Also, due to the wide variations intemperature within the digester, the contraction and expansion of the common rigidly -built and fastened strainers have caused. costly damages to the same.

' In my present'invention, I employ a strainer construction that permits the use of convenient sized strainer plates which may be removed quickly and easily for eicient cleaning. Also, the construction is such that the various elements of the assembled strainer can move freely with respect to each other thus eliminating the difficulties resulting from temperature stresses Y and strains.

Other objects and advantages of my invention will be apparent from the accompanying drawings and following detailed description.

In the drawings, Fig. l is a vertical elevational view of a digester, parts being broken away and parts beingshown in section.

Fig. 2 is a horizontal sectional view taken on line 2-2 of Fig. 1.

Fig, 3 is an enlarged transverse sectional view illustrating a portion of my strainer construction.

Fig. 4 is an enlarged detained horizontal seetion showing various details of my strainer construction.

Fig. 5 is a detailed elevational view of a por-- tion of the strainer construction.

Referring in detail to the drawings, l indicates a chemical pulp digester which comprises a metal shell 2 which is usually dome-shaped at its upper portion as indicated at 3 and tapered conically at its lower portion as rindicated. at 4. A manhole 5 is provided adjacent the upper end of the digester whereby Wood chips and liquors utilized for the pulping of the chips may be introduced. Anoutlet 6 is carried at the lower portion of the conical tapered end i for the removal of the pulp. An outlet l is provided in the lateral wall of the digester i whereby gases and liquor may be removed from the digester. The'shell 2 of the digester is lined with an acid or corrosion resisting lining 8, preferably a refractory material.

In employing a digester such as digester i, wood chips are introduced into the digester and a liquor, frequently a dilute acid is also introduced into the digester, the liquor being adapted to react with the chips to produce what is known to the art as chemical pulp. In most digester constructions the liquor is introduced vinto the digester and withdrawn therefrom as'a continu ous operation. y l

In view of the fact that the digester is usually filled to capacity, to withdraw the liquor contemplates that some means be provided for withdrawing the liquor and gases without removing the chips or pulp. Consequently, the outlet for said liquor and gases is provided with a strainer which prevents such removal. A strainer construction for this purpose comprises the specific concept of my invention.

In my strainer construction channel members 9 and l0 are mounted upon the inner wall 8 of the digester. The channel members 9 and l0 are spaced vertically from each other` above andl below, respectively, the center line of the outlet 1. The channel members, of course, are curved to conform with the curved surface of the inner wall of the digester. members 9 and l0 to the inner wall of the di-l gester, bolts Il may be embedded and firmly grouted in the body of the lining 8, or'said bolts, if desired,- may extend entirely through the lining 8 and shell 2 and may be secured externally by means of nuts. 'This latter construction is not illustrated but is believed to be clear to aniI one skilled in. the art. The inner ends'of the To secure the channel' bolts II are threaded to receive nuts I2 whereby the channel members 9 and I0 are securely mounted upon the inner wall of the digester.

In mounting the channel members 9 and I 0 upon the digester wall, the same may be positioned thereon in sections. ',/It is contemplated that the members 9 and I0 may extend entirely around the circumference of the digester or may traverse any desired portion of the circumference. Therefore, the channel members 9 and III will be formed as arcuate sections which are disposed end to end to traverse a desired portion of the circumference of the digester. At one end of each channel member 9 a plate I3 (Figs. 4 and may be welded to the upper surface of the channel member, a portion of said plate extending beyond the end of the channel member whereby the same is adapted to slidingly overlap the end of an adjacent' channel member. Similarly a plate I4 is carried adjacent one end of the channel member IU and extends beyond the end thereof to overlap an adjacent channel member I0.

It can readily be seen that there is no rigid connection between the ends of adjacent channel members and that said channel members are free to expand or contract individually, excess contraction of the channel members leaving a large gap between adjacent channel members is compensated for by the provision of the plates I3 and I4 which tends to close the gap suiciently to prevent the passage of chips or pulp between the ends of the channel members.

Plain, arcuate plates I5 are adapted to be mounted upon channel members 9 and III, said plates being provided with relatively small apertures I6 which permit communication between the interior of the digester and annular space I1 provided between the inner wall of the digester and said plates. The outlet I communicates with this annular space to remove the liouors and gases which pass through the apertures I 6 in the plates I 5. Upon the inner faces of the plates I 5 adjacent the upper and lower edges thereof, angle irons I8 are mounted, said angle irons being adapted to register with the channel members 9 and I0 in an internesting fashion as shown best in Fig. 3. A plurality of plates I5 are utilized, said plates being curved to conform with the curvature of the channel members 9 and I0.

Adjacent plates I5 abut at their transverse edges and adjacent one transverse edge of each plate, a. lapping plate I9 is carried, said lapping plate being welded or otherwise secured to the plate I5. The lapping plate I9 extends beyond one transverse edge of each plate I5 and is adapted to slidingly overlap the transverse edge of an adjacent plate whereby excess contraction of adjacent plates resulting in a large gap between the transverse edges of .said adjacent plates is compensated by the plate I9 covering said gap to the extent necessary to prevent removal of chips and pulp into the annular opening I1.

y To mount the plates I 5 upon the channel members 9 and I I), substantially U-shaped clamping elements 20 and 2| are hooked over or engage the outer edges of the channel members 9 and I 0 and the upper and lower edges of the plate I5 respectively.

An opposite pair of clamping members 20 are secured together by a tie-rod 2| which is threaded as indicated at 22 at each of its ends for the reception of nuts 23, the arrangement being such that clamping members may be drawn into contact with the channel members 9 and I0, securely holding the plates I5 in position. As clearly shown in Figs. 1, 2 and 4, a. plurality of pairs of clamping members may be employed, .one pair of clamping members being disposed adjacent each end of a plate I5. 4

By employing this means of attachment or securement of plates I5 upon the channel mem- -bers 9 and I0, it can readily be seen that said plates will be rmly held in position, but that longitudinal movement of said plates with respect to the channel members 9 and I0 will be permitted since there is no positive connection between the plates I5 and the channel members 9 and I0. In addition, plates I5 can be readily removed for cleaning or replacement.

If the annular -space Il is to be defined around the entire circumference of the vessel, then ordinary plates I5 may be employed. If, however, the space I'I is to traverse only a portion of the circumference of the vessel, special plates-I5', Fig. 2, having inwardly extending ends 24, may be employed, the ends being adapted to close the opposite ends of the space I1. If desired, all of the plates defining the space I 'I may be perforated as in the case of plates I5, or alternate plates may be provided with perforations interposed between imperforate plates. Both types of plates are contemplated in my invention.

The channel members 9 and Il) may be formed.

with integral web and flanges or the same may be formed by separate strips welded at the corners as indicated at 25 in Fig. 3. Similarly the angles I B may be formed integral with the plates I5 and I5' or said angles may be Welded to the inner faces of said plates. In view of the fact that the chemicals introduced into the vessel I normally have a corrosive eiect upon metal, all of the metal parts contemplated in the construction of the strainer are of a non-corrosive type of metal.

I claim as my invention:

l. Chemical pulp digesting apparatus, comprising: a substantially cylindrical digester; a pair of supporting members positioned in vertically spaced relation upon the inner wall of said digester, said supporting members each carrying a flange along its inneredge, the flange of the upper supporting member extending upwardly and the flange of the lower supporting member extending downwardly; a perforated, plain, arcuate strainer plate bridging 'the space between said pair of spaced supporting members at their innermost flanged surfaces to provide a substantially concentric space between the inner wall of said digester and said plate; and clamping means frictionally holding said strainer plate in position relative to said flanges of said supporting members to thereby permit movement of said plate with respect to said supporting members, said digester being provided with an outlet opening communicating with said space, whereby iud from said digester passing through the perforations in said plate may be discharged through said outlet opening.

2. Chemical pulp digesting apparatus, comprising: a substantially cylindrical digester; a pair of arcuate channel memberssecured in vertically spaced relation upon the inner wall of said digester with the backs of said channel members opposing each other; a perforated, plain, arcuate strainer plate bridging said channel vmembers at their innermost flanged surfaces to provide a substantially concentric space between the inner wall of the digester and said plate; and clamping means frictionally holdingsaid strainer plate in position relative to the inner flange of said channel members to thereby permit movement of said plate with respect to said channel members, said digester being provided with an outlet opening communicating with said space, whereby iluid from saiddigester passing .throughthe periora tions in said plate may be discharged through said outlet opening. u

3. Chemical pulp digesting apparatus, comprising: a substantially cylindrical digester; apairoi supporting members positioned in spaced relationship upon the inner wall oi said digester; a perforated, plain, arcuate strainer plate bridging the space between said .pair of spaced supporting members to provide a substantially concentric space between the inner wall of the digester and said plate which is substantially rectangular in cross-section; and means for holding said plate in position upon said supporting members including apair of clamping elements engageable with said spaced supporting members and the opposite edges of said strainer plate and means for drawing said clamping elements-toward each other to irictionally hold said plate upon said spaced supacomt spaced supporting members, said digester being provided with an outlet opening communicating with said space,.whereby fluid from said digester passing through the perforations in said platemay be discharged through said outlet opening.

4. Chemical pulp digesting apparatus as denned in claim 3, in which the supporting members from arranged to engage at least the lower one porting-members while permittingrelative sliding movement oi said plate with respect to said of said supporting members to support the weight of said plate, whereby to relieve the clamping means of the burden of supporting the weight of said plate.

CHENEY K. BOYER. 

